An alternative placement of the keycard. This way, you'll always have it with you (or you'll have things more pressing to worry about if you do lose it).It's where I carry mine but it's sort of putting all your eggs in one basket. If I lose my phone, I lose my card too. Fortunately, I have another keycard in my wallet .
edit: The nice thing about the keycard-sandwiched-in-the-phone-case is that I can use it if I take too long to drive off and the car asks for a card to start. It does take an exact placement of the phone behind the cupholders for it to be recognized though. Probably the metal in the phone restricting the RFID reader's range. Same thing occurs if I try to use the phone against the B pillar reader. Useless to use my wallet (with keycard inside) as I have one of those RFID-blocking ones.